Complexes of hydrocarbylaluminoxanes with transition metal compounds have been found to be very effective olefin polymerization catalysts (Manyik et al. U.S. Pat. No. 3,242,099).
Hydrocarbylaluminoxanes can be made by the controlled partial hydrolysis of hydrocarbyl aluminum compounds. A problem encountered in doing this is the extremely high reactivity of the aluminum compounds. For example, trimethyl aluminum and triethyl aluminum react explosively with water. Even minor changes in the process can give a significant difference in the product. Accordingly, research on the preparation of hydrocarbylaluminoxanes has been directed at ways to control the reaction of hydrocarbyl aluminum compound with water so that it forms the desired aluminoxane having high activity when used as a co-catalyst and not insoluble gels or, worse yet, explosions.
A further problem is the difficulty in controlling the degree of polymerization of the hydrocarbyl aluminum. Aluminoxanes can exist in the form of linear or cyclic polymers. Each form and chain length can give different catalytic activity. The most difficult aluminoxane preparation to control is the synthesis of methylaluminoxane. Preparations carried out in apparently the same manner frequently lead to different products.
The simplest methylaluminoxane is tetramethylaluminoxane, (CH.sub.3).sub.2 AlOAl(CH.sub.3).sub.2. This can disproportionate to trimethyl aluminum and higher aluminoxane polymers. For this reason, long term storage of methylaluminoxane should be avoided.
Manyik et al., U.S. Pat. No. 3,242,099, report the preparation of alkylaluminoxane by adding water to an inert hydrocarbon solution of alkylaluminum at 0-100.degree. C., preferably 10-65.degree.) C.
Manyik et al. U.S. Pat. No. 3,300,458 disclose a continuous process for making hydrocarbylaluminoxanes by mixing a solution of a hydrocarbyl aluminum compound with a wet solvent at 5.degree. C. up to the boiling point of the solvent.
Kaminsky et al. U.S. Pat. No. 4,542,199 describe the preparation of methylaluminoxane by suspending CuSO.sub.4.multidot. 5H.sub.2 O in toluene and adding trimethyl aluminum to the suspension. The water of crystallization is less readily accessible and serves to moderate the reaction.
Kaminsky et al. U.S. Pat. No. 4,544,762 report a similar process using hydrated aluminum salts as the water source. Welborn, Jr., et al. U.S. Pat. No. 4,665,208 describe the same procedure but with other metal salt hydrates.
More recently, Schoenthal et al. U.S. Pat. No. 4,730,071 describe a process in which a solution of trialkyl aluminum in an inert solvent is added to an ultrasonically induced dispersion of water in an inert solvent to form an alkylaluminoxane. Schoenthal et al. U.S. Pat. No. 4,730,072 is similar except the water dispersion is formed using a high shear impeller.
Edwards et al. U.S. Pat. No. 4,772,736 disclose a process in which water is introduced below the surface of a solution of a hydrocarbyl aluminum compound at a location such that the water is immediately dispersed into the solution which is maintained at a temperature of 5-70.degree. C.